Bad news: The asteroid that just missed Earth is coming back. And...

NASA / JPL (Asteroid Gaspra 951-Objects in photo are larger than they appear)

In terms of a family car vacation, the ancient asteroid that flew by Earth Friday may have seemed far away -- 17,200 miles.

In astronomical terms, however, Asteroid 2012 AD 14 was actually very close, much closer, for example, than the Moon's 239,000 miles. And computer projections of that asteroid's Earth-like orbit into the future currently forecast an upcoming earthly encounter of the explosive kind. More on that disastrous possibility in a minute.

This asteroid was spotted by Spanish astronomers about a year ago. It's one of an estimated 500,000 near-Earth objects, only one percent of which have been cataloged. It's about half the size of a football field in length and from a distance looks much like a pumice stone.

A meteorite (which is what asteroids are called after entering Earth's atmosphere) that severely rattled Russians Friday morning was merely coincidental to the flyby. Ever heard a major meteor explosion? Turn up your volume and watch this video: (More text below)

And that Russian one was much smaller than the flyby, only an estimated 55 feet across and 10,000 tons of matter before starting its flaming plummet through the atmosphere, shattering and exploding to injure possibly as many as 1,000.

Asteroids hold interest for scientists because they are actual primordial debris, drifting galactic time capsules of minerals and matter created during the solar system's formation about 4.5 billion years ago. Those leftover clumps that didn't gravitate into forming planets have been flying about in the vacuum of space ever since, running into each other and cratering other planetary bodies like our Moon and Mars.

These dead rocks can pack quite a wallop. Ask the dinosaurs. When 2012 AD 14 flew by Earth at 2:24 P.M. Eastern time Friday, it was only 17,200 miles above Indonesia, tumbling along at almost five miles per second. With Earth itself moving through space at eight miles a second, the silent encounter was a brief one.

The passing asteroid actually penetrated inside the orbits closer to Earth than the geosynchronous satellites your TV signals bounce off. Those satellites hover in a tidy ring 22,200 miles above the Equator, a distance that means each circles at the same speed as the spinning planet beneath.

Because 2012 AD 14 flew through on a South to North plane, it never came closer than 5,000 miles to any satellite, according to the U.S. Air Force Space Command.

'Armageddon' (Bruce Willis will save us again)

NASA estimates the flyby asteroid was the largest to approach this close in more than a century.

On Earth it would weigh about 130,000 metric tons. That's even larger than one that tore through the atmosphere in 1908. It too preferred Russia. That meteorite explosion leveled 825 square miles, or 528,000 acres of Siberian forest.

However, Friday's uneventful visit was not without effects. The pull of Earth's gravity altered 2012 AD 14's orbit around the Sun, shortening its annual solar rotation from 366 Earth days to 317.

Based on current information, NASA scientists calculate the orbits of each known near-earth object out for the rest of this century.

For instance, 2012 AD 14's orbit will not bring it back to our neighborhood again until 2046, when Americans will still be paying for Barack Obama's recent borrowing.

Now, about that other bad news. According to the same computer calculations, in 2080 the orbit of 2012 AD 14, if unaltered in these next 67 years by some super-natural force like Bruce Willis, will slam into Earth at almost 18,000 miles an hour.

That explosive encounter, NASA says, will release about 2.5 megatons of energy into the atmosphere, causing "regional devastation."

Hopefully, that will occur over a desolate area like Siberia. Or Detroit.

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